Reaction of excess NO with the S = 3/2 Fe(III) complex (Et4N)(2)[Fe(PhPepS)(Cl)] (1) in protic solvents such as MeOH affords the {Fe-NO}(7) nitrosyl (Et4N)(2)[Fe(PhPepS)(NO)] (2). This distorted square-pyramidal S = 1/2 complex, a product of reductive nitrosylation, is the first example of an {Fe-NO}(7) nitrosyl with carboxamido-N and thiolato-S coordination. When the same reaction is performed in aprotic solvents such as MeCN and DMF, the product is a dimeric diamagnetic {Fe-NO}(6) complex, (Et4N)(2)[{Fe(PhPepS)(NO)}(2)] (3). Both electrochemical and chemical oxidation of 2 leads to the formation of 3 via a transient five-coordinate {Fe-NO}(6) intermediate. The oxidation is NO-centered. The ligand frame is not attacked by excess NO in these reactions.